AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

[GRAPHICS]The synthesis of the C-1,H-5 marine sponge alkaloids, (Z)-hymenialdisine and (Z)-2-debromohymenialdisine, is described. A key step was the condensation between aldisine or its monobromo derivative and a new, efficient imidazolinone-based glycociamidine precursor. In the first case, the main product turned out to be the unprecedented (+/-)-endo-2-debromohymenialdisine.

Reaction of the (5 R, 8 R)-ergoline derivative (6) with the couple CCl4/(Ph)(3)P unexpectedly resulted in the formation of the novel (5 S, 8 R)-5 (10-->9)abeo-ergoline derivative. A mechanism of this transposition process is proposed.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

At variance with their Parent sulfides, cephem-1beta-sulfoxides are smoothly and steroselectively alkoxylated at C-4 upon reaction with cerium ammonium nitrate in the suitable alcohol. Moderate yields were obtained with cephem sulfones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A thiyl radical cyclization approach to the sulphur containing ring of cephams is described. The reaction was carried out using metals able to perform a single-electron oxidation process under stoichiometric [Fe(III), MN(OAc)3] or catalytic [Fe(III)] conditions. Furthermore, the FeCl3 or Mn(OAc)3/LiX promoted reactions afforded, by a double single-electron oxidation process, over oxidized compounds. The relationship with the mechanistic hypothesis proposed by Baldwin for the DAOC/DACS-catalyzed ring expansion from Penicillin N to Desacetoxy cephalosporin C is discussed.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Functionalization of the dihydrothiazine ring of cephem esters and 4-ketones was studied at the sulfone oxidation level. On the esters, alkylation and Michael addition gave 4beta- and 2alpha,4beta-substituted products. On the ketones, electrophilic insertion of carbon, halo, oxygen and sulfur substituents was achieved with acceptable selectivity at 2alpha. Nucleophilic sulfenylation and acyloxylation was successful on 2-bromocephem ketones, themselves electrophilic bromination products. Noticeable events included shift of the 3-cephem double bond and epimerization at C-2. Configurations and ring conformation were evinced by nmr studies. Several compounds were potent inhibitors of human leukocyte elastase.

Construction of the penam ring system has been achieved by dirhodium tetraacetate cyclization of 4-thio-1H-azetidinone derivatives bearing an a-diazoester appendage. The sulfur atom of 4-thioethers interferes by reacting with the electrophilic metal carbene, but the corresponding sulfone and sulfoxides undergo the prescribed cyclization exclusively. Nmr studies on obtained bisnorpenams indicate pseudoequatorial puckering for the thiazolidine ring of the S-sulfoxide, while the parent sulfide and the R-sulfoxide exist as pseudoaxial conformers

The molecular event ensuing from β-lactam cleavage of cephem sulfones by chemical nucleophiles have been determined. Alkaline hydrolysis and methanolysis led to opening of the dihydrothiazine ring to produce sulfinate salts. Cleavages promoted by NaN3, imidazole and n-PrSH in MeCN gave products from dihydrothiazine opening and desulfonylation. By contrast with enzyme-promoted reactions, expulsion of potential leaving groups at C3′ was not observed.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Upon cleavage of the beta-lactam ring, penems are converted to unstable DELTA(4)-thiazolines, which epimerize at the ex-C-5 position, lose a nucleofugal group at C-2' (if originally present), tautomerize to DELTA(3)-thiazolines, or suffer hydrolytic decomposition. Other chemical events, observed on some substrates under determinate conditions, include protomeric and oxidative aromatization to thiazoles (followed by side-chain reactions, such as epimerization at C-6, decarboxylation, dehydration, retro-aldol condensation), and conjugate addition of external and internal thiols. Mention is made of the chemical, biochemical and pharmacological significance of these findings.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The H-1 NMR spectra of cephem sulphones, independently of the type and orientation of the side chain at C-7, are characterized by a long-range coupling between H-6 and H-2-alpha. Other spectral evidences, including the NOEs observed for H-6 to H-2-alpha and for 3-CH3 to H-2-beta, indicate that the compounds exist in solution as << open >> dihydrothiazine conformers. The origin of this coupling is attributed to a sigma-pi orbital overlap in the system formed by the two axial protons and the central S = O bond. Use of this phenomenon is proposed as a simple diagnostic tool for determining the stereochemistry of cephem sulphones monosubstituted at C-2, which are potent inhibitors of human leukocyte elastase.

The direct conversion of 7-ADCA into the corresponding 7α-alkoxy derivatives is described. This reaction constitutes the most convenient access to a new class of potent inhibitors of human leukocyte elastase.

Two azetidinyl benzothiazolyl disulphides, 3 and 8, were found to rearrange to 2β-(benzothiazolylthiomethyl)penams upon thermolysis in toluene. When an external acid catalyst was added, the reaction became general and could be used as a synthetic cool.